The detection of the level of glucose or other analytes, such as lactate, oxygen or the like, in certain individuals is vitally important to their health. For example, the monitoring of glucose is particularly important to individuals with diabetes. Diabetics may need to monitor glucose levels to determine when insulin is needed to reduce glucose levels in their bodies or when additional glucose is needed to raise the level of glucose in their bodies.
Devices have been developed for the in vivo monitoring of analytes such as glucose in bodily fluid such as in the blood stream or in interstitial fluid over a period of time. These analyte measuring devices include in vivo analyte sensors that are positioned in vivo, e.g., below a skin surface of a user in a blood vessel or in the subcutaneous tissue of a user during the testing.
Blood vessel sensors are more invasive than subcutaneous sensors, but have the advantage of providing analyte concentrations directly from the blood. Subcutaneous analyte sensors are therefore used, but they too have certain limitations. For example, the insertion of the analyte sensor in the subcutaneous tissue results in skin and/or tissue trauma, which in turn provokes an immunological response that can cause inaccurate sensor readings, at least for a period of time. For example in the case of glucose sensors, the trauma may cause an over-consumption of glucose in the positioned sensor vicinity by erythrocytes released by localized bleeding. Further, the glucose response from a subcutaneously positioned sensor lags the response of a venously positioned sensor, primarily due to a physiological lag between subcutaneous and venous glucose.
It would therefore be desirable to have devices and methods that address these issues and that accurately monitor analyte levels, such as glucose, in areas of the body other than blood vessels or the subcutaneous tissue.